1. Field of the Invention
The present invention relates to a wheel having a compensated and controlled pressure.
2. Description of the Related Art
A wheel for two-wheeled or four-wheeled vehicles generally comprises a rim coupled with a tyre that is inflated to a given operating pressure.
Said tyre generally comprises a carcass structure having at least one carcass ply, and at least one annular reinforcing structure associated with the carcass ply, a tread band of elastomer material at a radially external position to the carcass structure, a belt structure interposed between the carcass structure and tread band and a pair of sidewalls at axially opposite positions on the carcass structure.
In tubeless tyres, the tyre airtightness is ensured by the radially inner layer of said carcass structure generally called “liner”. When in use, due to the natural air loss through said radially inner layer (which layer at all events is never perfectly impervious to air), pressure within the tyre decreases thereby obliging the vehicle driver to carry out periodical restoration of same.
In an attempt to make the tyre pressure substantially constant over a rather long period of time, it was suggested use of rims internally housing a tank for gas under pressure at a higher pressure than the operating pressure of the tyre. By one or more valves suitably operated, pressure is restored when required.
Patent U.S. Pat. No. 6,601,625 B2 discloses a wheel with a compressed air tank integrated into the rim. More specifically it is disclosed a high pressure tank to store compressed air from an outer source, a first mechanical valve allowing the compressed air to flow from a source external to the high pressure tank, a second mechanical valve allowing air passage from the high pressure tank to the inner tube of the tyre, a third valve releasing air from the inner tube of the tyre, and a fourth valve releasing air from the high pressure tank. The wheel described in said patent keeps the tyre pressure within a predetermined value in a mechanical manner, reducing the necessity for the vehicle driver to manually inflate the tyre to reach the desired pressure. When pressure within the tyre decreases under a predetermined threshold value, the air stored in the high pressure tank is released into the tyre maintaining the latter inflated to the desired minimum pressure; on the contrary, when pressure in the tyre increases beyond a predetermined threshold value, the air is released from the tyre to the surrounding atmosphere.
Patent U.S. Pat. No. 4,067,376 depicts a system for automatic re-admission of the air lost from a tyre while the vehicle is running in order to minimise the effects of an explosion. The wheel is formed with an integrated annular bag adapted to store an amount of compressed air under high pressure. A pressure safety valve is placed between said bag and the tyre and is adapted to release air from the bag to the tyre each time pressure within the tyre decreases below a predetermined limit.